1. Field of the invention
The present invention relates to a feedthrough type three-terminal electronic component having a monolithic structure formed by stacking one or more pairs of an internal signal electrode and an internal ground electrode so as to face one another across a dielectric layer, a pair of external signal electrodes which are connected to extension portions of the internal signal electrodes, and an external ground electrode connected to internal ground electrodes.
2. Description of the Related Art
FIGS. 6A and 6B, 7A and 7B, and 8 illustrate a feedthrough type three-terminal electronic component (feedthrough type three-terminal capacitor) which is a type of a monolithic electronic component.
Here, FIG. 6A is a front cross-sectional view of a conventional feedthrough type three-terminal electronic component, FIG. 6B is a side cross-sectional view thereof, FIG. 7A is a plan view illustrating the form of an internal signal electrode, which is an element of a conventional feedthrough type three-terminal electronic component, FIG. 7B is a plan view illustrating the form of an internal ground electrode, and FIG. 8 is a perspective view illustrating the external configuration of a conventional feedthrough type three-terminal electronic component.
The feedthrough type three-terminal electronic component has a structure wherein, a monolithic structure 54 (FIG. 8) is formed by stacking an internal signal electrode 52 (see FIG. 7A) and an internal ground electrode 53 (see FIG. 7B) so that the principal portions thereof face one another across a dielectric layer 51 as shown in FIGS. 6A and 6B. In addition, as shown in FIG. 8, a pair of external signal electrodes 55a and 55b (FIG. 6A) to which the extension portions 52a and 52b of internal signal electrodes 52 are connected is disposed on both end surfaces of the monolithic structure 54, and an external ground electrode 56 (FIG. 6B) to which the extension portions 53a and 53b of internal ground electrodes 53 are connected is disposed on both side surfaces of the monolithic structure 54.
Now, with a feedthrough type three-terminal electronic component (feedthrough type three-terminal capacitor) having such a structure, normally, the electronic component includes a predetermined number of ceramic green sheets 57 upon which is disposed an internal signal electrode (pattern) 52 as shown in FIG. 7A and ceramic green sheets 58 upon which is disposed an internal ground electrode (pattern) 53 as shown in FIG. 7B being alternately layered, and further, outer layer ceramic green sheets (not shown) with no internal electrodes disposed thereon being layered on both the top and bottom and surfaces, and subjected to the processes of compression and baking, so that, as shown in FIGS. 6A and 6B, internal electrodes (the internal signal electrodes 52 and internal ground electrodes 53) are layered with high concentration at the region X (electrode layering region) wherein the internal signal electrodes 52 and internal ground electrodes 53 are layered, but at the regions Y (extension portion layering region for signals) wherein the extension portions 52a and 52b of the internal signal electrodes 52 are disposed, and at the regions Z (extension portion layering region for grounding) wherein the extension portions 53a and 53b of the internal ground electrodes 53 are disposed, the internal electrodes (extension portions 52a and 52b and extension portions 53a and 53b) are disposed at every other layer (sparsely), meaning that there are irregularities in the layering concentration (distribution concentration) of the internal electrodes.
Consequently, at the time of baking the monolithic structure, scattering at the internal electrodes partially and selectively increases, so the sintering state of the internal electrodes becomes non-uniform, resulting in a problem wherein there are irregularities in the resistance of the internal electrodes.
Particularly, the sintering tends to be insufficient in the signal extension portion layering regions Y and the grounding extension portion layering regions Z, and connection with the external signal electrodes 55a and 55b and the external ground electrode 56 becomes poor, so there has been a problem in that the DC resistance tends to fluctuate.
Also, the resistance of the internal signal electrodes and the internal ground electrodes normally tends to become high in the event that sintering is insufficient, but these characteristics also become high in the event that sintering is excessive, and the irregularities in concentration on the monolithic structure due to the disposed state of the internal signal electrodes and grounding causes insufficient or excessive sintering, and is a great factor leading to fluctuations in the DC resistance.
In order to overcome the problems described above, preferred embodiments of the present invention provide a highly reliable feedthrough type three-terminal electronic component having a monolithic structure including internal signal electrodes and internal ground electrodes stacked so as to face one another across a dielectric layer, wherein the sintering state of the monolithic structure is uniform and DC resistance is very small.
According to a first preferred embodiment of the present invention, a feedthrough type three-terminal electronic component includes a monolithic structure having one or more pairs of an internal signal electrode and an internal ground electrode stacked so as to face one another across a dielectric layer, external signal electrodes communicating with extension portions of the internal signal electrodes and disposed on both end surfaces of the monolithic structure, and an external ground electrode communicating with extension portions of the internal ground electrodes and disposed on both side surfaces of the monolithic structure, wherein internal dummy electrodes, which essentially do not contribute to electrostatic capacity formation, are disposed in at least one of: (a) a region defined by both side portions of the internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion; and (b) a region defined by both side portions of the internal ground electrodes and the external signal electrodes provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion.
Disposing internal dummy electrodes which essentially do not contribute to electrostatic capacity formation in at least one of a region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion, and a region defined by both side portions of internal ground electrodes and external signal electrodes provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion, suppresses irregularities in the concentration of internal electrodes disposed within the monolithic structure and makes the sintering state of internal electrodes at the time of baking the monolithic structure uniform, thereby enabling irregularities in the resistance of internal electrodes to be minimized and prevented.
That is, with the feedthrough type three-terminal electronic component according to preferred embodiments of the present invention, there are few irregularities in the concentration of internal electrodes, imbalance in the state of disposal of internal electrodes in the monolithic structure formed by alternately stacking internal signal electrodes and internal ground electrodes across dielectric layers (ceramic green sheets) and compressing in the manufacturing process is prevented from occurring, thereby preventing irregularities in the compression state and making the sintering state uniform. Accordingly, a feedthrough type three-terminal electronic component with small DC resistance and high reliability can be obtained in a highly reliable manner.
Further, providing internal dummy electrodes increases the area of contact between the external signal electrodes and internal signal electrodes, and the area of contact between the external ground electrode and internal ground electrodes, thereby increasing the adhesion strength of the external electrodes, while the increased area of contact reduces the contact resistance, thereby improving anti-surge properties.
Now, with preferred embodiments of the present invention, the phrase xe2x80x9ca region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashionxe2x80x9d is a concept meaning a region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion, regardless of whether on the same plane in the monolithic structure where an internal signal electrode is disposed or on a different plane. This is a broad concept including not only feedthrough type three-terminal electronic components manufactured by a process wherein, for example, internal dummy electrodes are disposed on the same ceramic green sheets where internal signal electrodes are disposed, and the ceramic green sheets are layered, of course, but also to feedthrough type three-terminal electronic components manufactured by a process wherein internal dummy electrodes are disposed on different ceramic green sheets from those where internal signal jog electrodes are disposed, and the ceramic green sheets are stacked.
Further, the concept of xe2x80x9ca region defined by both side portions of internal ground electrodes and external signal electrodes provided on both end surfaces of the monolithic structure, viewing the monolithic structure in planar fashionxe2x80x9d is also a broad concept in the same way as with the above-described region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure.
Moreover, with preferred embodiments of the present invention, the internal dummy electrodes may or may not be in a state of conducting with the external signal electrodes and the external ground electrode. However, a situation wherein the internal dummy electrodes are in a state of conducting with the internal signal electrodes and internal ground electrodes is undesirable, since the internal dummy electrodes will greatly contribute to electrostatic capacity formation.
Also, according to a second preferred embodiment of the present invention, a feedthrough type three-terminal electronic component includes a monolithic structure including a stack of one or more pairs of an internal signal electrode and an internal ground electrode, facing one another across a dielectric layer, external signal electrodes communicating with extension portions of internal signal electrodes and disposed on both end surfaces of the monolithic structure, and an external ground electrode communicating with extension portions of internal ground electrodes and disposed on both side surfaces of the monolithic structure, wherein internal dummy electrodes, which essentially do not contribute to electrostatic capacity formation, are disposed in both: (a) a region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion, and (b) a region defined by both side portions of internal ground electrodes and external signal electrodes provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion.
Disposing internal dummy electrodes which essentially do not contribute to electrostatic capacity formation in both a region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion, and a region defined by both side portions of internal ground electrodes and external signal electrodes provided on both side surfaces of the monolithic structure, viewing the monolithic structure in planar fashion, enables irregularities in the concentration of internal electrodes disposed in the monolithic structure to be prevented and eliminated, thereby making the sintering state of internal electrodes at the time of baking the monolithic structure uniform.
Further, the area of contact between the external signal electrodes and internal signal electrodes and the area of contact between the external ground electrode and internal ground electrodes increases, such that increases in contact resistance are minimized and prevented in an even more reliable manner, and consequently, the completed product has excellent anti-surge properties.
Also, regarding the internal dummy electrodes, internal dummy electrodes, disposed in a region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, may have a form essentially corresponding to the form of the extension portions of internal ground electrodes, and may have dimensions extending in the direction following both side surfaces of the monolithic structure which are essentially the same as or greater than the width of the extension portions of the internal ground electrodes. Alternatively, internal dummy electrodes, disposed in a region defined by both side portions of internal ground electrodes and external signal electrodes provided on both side surfaces of the monolithic structure, may have a form essentially corresponding to the form of the extension portions of internal signal electrodes, and may have dimensions extending in the direction following both end surfaces of the monolithic structure which are essentially the same as or greater than the width of the extension portions of the internal signal electrodes.
This arrangement wherein, of the internal dummy electrodes, internal dummy electrodes, disposed in a region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, have a form essentially corresponding to the form of the extension portions of internal ground electrodes, and have dimensions extending in the direction following both side surfaces of the monolithic structure which are essentially the same as or greater than the width of the extension portions of the internal ground electrodes, and internal dummy electrodes, disposed in a region defined by both side portions of internal ground electrodes and external signal electrodes provided on both side surfaces of the monolithic structure, have a form essentially corresponding to the form of the extension portions of internal signal electrodes, and have dimensions extending in the direction following both end surfaces of the monolithic structure which are essentially the same as or greater than the width of the extension portions of the internal signal electrodes, enables the disposed state of the internal electrodes to be even more uniform, achieving further advantages of the present invention.
The reason that the dimensions of the internal dummy electrodes in the above-described predetermined direction are preferably the same as or greater than the width of the extension portions of the internal ground electrodes or internal signal electrodes is that this structure results in each of the electrodes being sandwiched between dummy electrodes from above and below, thereby facilitating making uniform the sintering state of the internal electrodes.
In an alternative arrangement, the internal dummy electrodes may be disposed only in the region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, and may not be disposed in the region defined by both side portions of internal ground electrodes and external signal electrodes provided on both side surfaces of the monolithic structure.
With the arrangement wherein internal dummy electrodes are disposed only in the region defined by both side portions of internal signal electrodes and the external ground electrode provided on both side surfaces of the monolithic structure, the sintering state is made uniform to a degree which is sufficiently meaningful for actual use, and the DC resistance is greatly reduced. This is because the width of the extension portions of the internal ground electrodes is smaller than the width of the extension portions of the internal signal electrodes, and accordingly is more readily affected by sintering of the internal electrodes.
Also, Ni or a Ni alloy may be used as a material for forming the internal signal electrodes and the internal ground electrodes.
In the event that Ni or a Ni alloy is used as the material for forming the internal signal electrodes and the internal ground electrodes, irregularities in the sintering state occur more readily due to imbalance in the state of internal electrodes disposed in the monolithic structure, since Ni scatters more readily than Pd at the time of sintering, but the sintering state can be made uniform and the DC resistance reduced by applying preferred embodiments of the present invention in such a case, which is particularly significant.
Also, the thickness of the internal signal electrodes, the internal ground electrodes, and the internal dummy electrodes, may be about 2 xcexcm or less.
As the number of layers of internal electrodes increases, the thickness of the internal signal electrodes, internal ground electrodes, and internal dummy electrodes often becomes thinner, and in the event that the thickness of the internal electrodes including the extension portion is about 2 xcexcm or less, great fluctuations in DC resistance readily occur due to the sintering state of the internal electrodes, but in such a case, applying preferred embodiments of the present invention allows a feedthrough type three-terminal electronic component to be obtained with a uniform sintering state and small DC resistance, which is particularly significant.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the attached drawings.